Carbon can be used on a new aquarium including through the biological cycling process. This can be useful for soaking up stray organics during this time.

The useful life of a good quality carbon, such as ROWA carbon, is around 7-14 days. It can be changed after this time so that a small ammount is used constantly or it can be replaced less frequently, if the carbon is not required full time.

Its best put the carbon in a media bag and rinse with some RO or old tank water to remove any fine dust before adding to the aquarium. Active carbon, such as the ROWA carbon, will fizz initially when it contacts water, this is normal as air exits the pores of the media.